Objective To investigate the clinical value of low tube voltage (100kVp) , low concentration contrast medium(270mgI/mL) and Adaptive Iterative Dose Reduction 3D in cerebral-and-cervical CT angiography (CTA) with 320-slice CT scanner. Methods The cerebral-and-cervical CTA data of Sixty patients which were suspected as cerebral and cervical vascular disease were collected and the patients were divided into two groups randomly. Patients in group A were performed CTA by using low tube voltage (100 kVp), low concentration contrast medium(270mgI/mL), with the Sure Exposure 3D automatic exposure control system and AIDR 3D reconstruction. Patients in group B using 120 kVp tube voltage, contrast medium of Ultravist (370mgI/mL), with filter back projection (FBP) reconstruction. Statistic analysis was implemented with regard to the CT values, the image quality and the radiation dose values. Results The CTDIvol and DLP reduced 48.5%,50.8% respectively in group A (5.3±0.9)mGy vs 0.3±1.4)mGy ,(191.0±37.6) mGy×cm vs (388.1±45.4)mGy×cm, the differences had statistic significance (P<0.05). The subjective evaluation of the images and CT value of group A were higher than group B, and the differences were statistically significant (P<0.05). The SNR and CNR of the aorta were higher in group B than in group A, the differences were in statistic significance (P<0.05). There was no significant statistic difference between group A and group B for the SNR and CNR of the common carotid artery, the internal carotid artery and the middle cerebral artery. Conclusion Cerebral-and-cervical CTA with low tube voltage and low-concentration contrast by AIDR 3D reconstruction performs higher quality image, and reduces the radiation dose for the patients greatly without image affect for diagnosis.